You may consider other colors. OCRichard has demonstrated that claret looks very nice with the Isle of Skye tartan. Grey is also a nice color, either the dark charcoal or the mid-grey looks good with this tartan. And I've seen several shades of green that look nice with this tartan, as well. Because the Isle of Skye tartan itself has three different greens in it, green hose tend to find something there to tone with, be they bottle/tartan green, loden green, or lovat green.
And if you do go with a green (or other colour), perhaps you could find purple garter ties to kinda-sorta go for the same look you were originally trying? STM does list purple garter ties, though I don't know if they're in stock either.